There has been proposed an image-forming apparatus that includes a main housing, a photosensitive drum supported to the main housing, and a cartridge provided with a developing roller. The cartridge is attached to and detached from the main housing.
As one of such image-forming apparatus, Japanese Patent Application Publication No. 2012-68371 discloses an image-forming device including: a cartridge having a positioning boss protruding outward in an axial direction of a developing roller; and a main housing formed with a receiving groove adapted to guide the positioning boss, so that the cartridge can be attached to the main housing. An urging member is provided in the receiving groove for urging the positioning boss toward downstream in a cartridge attaching direction so that the developing roller is brought into abutment with the photosensitive drum.